Technical Field
The present disclosure relates to a toner for developing electrostatic images, an image forming apparatus, an image forming method, a process cartridge, and a developer.
Description of the Related Art
In image forming apparatuses such as electrophotographic apparatuses and electrostatic recording apparatuses, an image is formed by developing an electrostatic latent image formed on a photoreceptor into a toner image with toner; transferring the toner image onto a recording medium such as paper; and fixing the toner image thereon by application of heat. A full-color image is generally formed by transferring four toner images of black, yellow, magenta, and cyan onto a recording medium to superimpose them one another, heating the superimposed toner images to melt them simultaneously, and fixing the composite color image on the recording medium.
Toner is required to be fixable at much lower temperatures to achieve an objective of global environmental load reduction. One approach for improving low-temperature fixability of toner involves lowering softening characteristics of the toner, but this approach causes a decrease in heat-resistant storage stability of the toner. When such a toner with poor heat-resistant storage stability is melted under high-temperature and high-humidity environment and then returned to room temperature, the toner will be solidified and unable to exert its inherent fluidity. Moreover, such a toner is likely to melt and slightly adhere to fixing members at around the upper limit temperature of the fixable temperature range (this phenomenon is hereinafter referred to as “hot offset”). It is very difficult for toner to achieve a good balance between low-temperature fixability and heat-resistant storage stability.
Toner is also required to be fixable on various kinds of recording media at low temperatures. For example, in a case in which a toner exists on a concave portion of paper having a large degree of surface roughness and cannot receive sufficient pressure from a fixing member, it is preferable that the toner can spread to some extent only by heat from the fixing member to increase the contact area with the paper, which prevents generation of abnormal images such as slight-amount cold offset. Toner is required to have adaptability to various kinds of recording media with high reliability.